One approach to reducing drug use and abuse is to identify factors that differentiate current users from nonusers (never-users and ex-users) and then to determine whether the factors in question are causally associated with the drug use. If they are causally related, this information may be used to identify at-risk populations, to develop targeted treatments or interventions and to understand how drug exposure impacts brain function. Impulsivity may be one of those factors. A growing body of literature indicates that drug users are more impulsive than nonusers, where impulsivity has been defined variously as a reduced ability to delay gratification or to inhibit behavior, heightened risk- and sensation-seeking, acting without weighing the consequences appropriately, etc. However, the direction of causality between impulsivity and drug use is unclear, and the mechanisms underlying this relationship are unknown. High levels of impulsivity might cause people to experiment with cigarettes, and then continue to use. Alternatively, the actions of nicotine might acutely or chronically increase impulsive decision-making. Indeed it is possible that both processes may be involved - heightened impulsivity precipitating smoking initiation, then doses of nicotine increasing impulsive decision-making, which in turn decreases the likelihood of successful quitting. The current proposal outlines 5 experiments that will address the relationship between impulsivity and several different aspects of drug use using cigarette smoking (nicotine) as the model of drug use under investigation. The first 3 studies examine the relationship between baseline measures of impulsivity and smoking cessation treatment outcomes (Study 1), the subjective aversiveness of short-term withdrawal and relief from withdrawal (Study 2), and the intensity of cigarette smoking (Study 3). These studies will result in a better understanding of how general behavioral traits (a.k.a. personality) can impact how drugs are used and how those traits influence their continued use. The final 2 studies examine how state measures of impulsivity, assessed using laboratory tasks to assess impulsive decision-making, are affected by abstinence from nicotine (Study 4) and increases in systemic nicotine in smokers and nonsmokers (Study 5). It is hoped that these studies will result in a better understanding of the factors impacting drug use and how drug use can impact decision-making.